Finned liquid particles separator

ABSTRACT

A separator disposed in parallel relationship is provided for separating liquid particles entrained in a gas stream. It comprises zigzag walls (25) having fins (27) each covering each of the convex folds (28) of the walls while forming an open scoop (29) facing the gas flow. Each fin has a portion (27a, 27b) parallel to the wall (25) which supports it and which is spaced apart from said wall upstream and downstream of the fold (28). A rear connection zone (27c) gradually joins the wall and is connected along a line located substantially in the same plane orthogonal to the two walls defining a channel for the gas flow than the leading edge of the following fin (27).

BACKGROUND OF THE INVENTION

The present invention relates to an apparatus for separating entrainedliquid particles from a stream of gas of the type having an enclosure inwhich are disposed a plurality of generally parallel partitions of zigzag horizontal cross-sectional shape distributed at even intervals anddefining a plurality of inter-partitions channels constitutingrespective sinuous travelling paths for said stream of gas.

It relates particularly to an apparatus or separator whose partitionscarry fins covering each convex fold of said partitions, each finforming with its supporting partition an open scoop facing the gas flow.

The invention is particularly, also not exclusively, suitable for highefficiencies eliminators used for natural circulation steam generatorsof nuclear reactors.

Gas-liquid separators of the above defined type are already known. Thedocument FR-A-No. 1 541 045, relating to a device for separating liquidfrom a gaseous fluid, shows a separator construction in which partitionsor "blade elements" present regular series of successive convex foldsand concave folds. Fins are fixed on each convex fold and extend fromsaid fold in the direction of the gas flow for collecting or trappingthe liquid.

This type of separator, although it presents a high efficiency for adrop size distribution with size larger than the limit drop size toconsider, has the drawback of important pressure drops for a given flowrate.

The limit drop size is the size of the smallest drop which, for givenseparator construction, gas velocity and characteristics of the liquidand gas involved, can just be completely eliminated.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an improved separator of theabove defined type; it is a more particular object to provide a highefficiency liquid gas separator for a given limit drop size presentinglow pressure drops.

For this purpose, the invention provides an apparatus having anenclosure, a plurality of generally parallel partitions of zigzaghorizontal cross-sectional shape distributed at even intervals withinthe enclosure and defining a plurality of inter-partition channelsconstituting respective sinuous travelling paths for said stream of gas,each of said paths having alternated bends each defined by a concavevertical fold of one of the partitions defining the path and a convexvertical fold of the other partition defining the path, each of saidconvex vertical folds being provided with a respective verticallyextending channel defining a fin. Each of said fins has a first portioncovering the respective convex fold, substantially parallel to saidrespective convex fold and at a distance thereof over a length which isa fraction of the distance between two successive folds, (i.e. a convexand a concave folds on the same partition) therefore defining an openscoop having a leading edge and facing the gas flow, and a secondportion fixed to the corresponding supporting partition said secondportion progressively joining said partition until reaching thepartition along a "root" line on the downstream part of the fold coveredby the fin, said root line being substantially located in the same planorthogonal to the two partitions defining the channel than the leadingedge of the next downstream following fin covering the downstreamfollowing fold of the opposite partition of said channel. The firstportion of each fin is in spaced relationship with its supportingpartition, said first portion covering the convex fold on a certaindistance upstream and a certain distance downstream from the sumit ofsaid convex fold.

The invention also provides an apparatus for separating entrained liquidparticles from a stream of gas which flows in a general horizontaldirection comprising an enclosure and a plurality of generally parallelpartitions of zigzag horizontal cross-sectional shape distributed ateven intervals within said enclosure and defining a plurality ofinter-partition channels constituting respective sinuous travellingpaths for said stream of gas, each of said path having alternate bendseach defined by a concave vertical fold of one of the partitionsdefining the paths and a convex vertical fold of the other partitiondefining the path, and each of said convex vertical folds being providedwith a respective vertically extending channel defining a fin forming anopen scoop with said partition wherein the fins of a same channel arearranged to define with the opposite corresponding partition of saidchannel a substantially constant flow section for the gas flow all alongthe path of said gas flow in said channel.

In an advantageous embodiment, each fold of the zigzag partitions orwalls is formed by a single bend.

In a preferred embodiment, each fin is connected to the correspondingpartition by a distal end having a bend part which matches the shape ofsaid partition over a length including the following concave verticalfold succeeding the convex vertical fold covered by said fin.Advantageously, each fold forming bend of the zigzag partitions is asharp angled dihedron.

In order to easily connect together the different zigzag partitions, ina preferred embodiment, each zigzag partition is provided with at leastfour spacer elements disposed at the periphery of said partitions, eachof the spacer elements having an aperture on one side and a stud on theother side, the studs of the spacer elements of a partition beingarranged for insertion in the corresponding apertures of the spacerelements of the adjacent partition for connection.

This allows an even spacing between the partitions.

This spacing is determined so as to prevent the gas stream or flow frompassing directly between two adjacent finned walls or partitions. Thedifferent partitions or walls may be maintained in position by thefollowing advantageous arrangement: the zigzag partitions are fittedbetween two plates, one of the plates being supported on a first wall ofthe enclosure and the other being pressed and maintained with screwswhose threads engaged the opposite wall of the enclosure, the head ofsaid screws being connected together with small plates, blades or rods.

SHORT DESCRIPTION OF THE DRAWINGS

The invention will be better understood from reading the followingdescription of a particular embodiment, given by way of non limitativeexample. The description refers to the accompanying drawings in which:

FIG. 1 is a schematical view in vertical section of the upper part of asteam generator of a pressurized water nuclear reactor havingapparatuses of the type described in the invention.

FIG. 2 is a sectional view through II--II of FIG. 1 of the separatoraccording to the invention.

FIG. 3 is a sectional view through III--III of FIG. 1 of a separatoraccording to the invention, and

FIG. 4 is a view on a larger scale showing the detail of a channelseparating the two finned walls of the separator of the invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

FIG. 1 shows schematically in section the upper part of a steamgenerator equipping each main steam line of the cooling circuit of apressurized water reactor.

The steam generator comprises an enclosure 1, an evaporator assembly 2formed by a bundle of tubes 3 (partially shown) disposed in the form ofan upturned U and through which flows the primary pressurized waterwhich comes from the vessel of the reactor and which penetrates into thegenerator and leaves through the bottom of the generator (not shown).

These tubes 3 are mounted in a cylindrical casing 4 having spacer plates6 pierced with holes 5, some of which are used for letting tubes 3 passtherethrough and for holding them in position.

Antivibratory spacers 7 further hold tubes 3 in position in their bentpart. The water of the secondary coolant circuit, to be vaporized fordriving a turbine, is fed into the generator through an inlet pipe 8 andis distributed over the periphery of the steam generator by the supplyring 9 in the water supply zone 10.

The generator further comprises at the top part at least one humidityseparator 11 of known type, including a fan 12 and a cylindrical wall13.

Above the humidity separators 11 are disposed two stages 14 and 15 ofseparators according to the invention, each formed by four separators 16of the invention, said separators forming the eight vertical walls oftwo parallelepipeds whose inside are directly related to the steamoutlet pipe 17.

Referring to FIGS. 2 and 3, which represent the separator 16respectively in vertical section and in horizontal section, theseparator includes an enclosure 18 with an inlet dividing wall 19 havingholes 20 and/or fixed vanes 23 for orientating the streams of the steamflow penetrating into the separator 16.

Under the water-steam separation zone 21 is disposed a water collectingzone 22. This water is evacuated through tubes 24 which open into thewater supply zone 10 of the generator.

The separation zone 21 includes parallel walls 25 having a zigzagconfiguration and defining therebetween flow channels 26 for the steam.The zigzags are formed by bending metal plates.

Partitions or walls 25 carry fins 27 in accordance with the invention,covering each inwardly directed or convex fold 28 of each channel, thefolds forming sharp edged dihedrons. Each fin forms an open scoop 29facing the gaseous flow.

In FIG. 3, and for simplifying, only four walls have been shown.

Each fin 27 (FIG. 4) has a first portion having two parts 27a and 27bparallel to the wall 25 which supports it, upstream (27a) and downstream(27b) of the summit of the convex fold 28 covered. The first portion isextended by a rear connection zone or second portion 27c graduallyjoining wall 25 and connected thereto along a root line substantially inthe same plane orthogonal to the two partitions defining the channelthan the leading edge of the immediate downstream following fin in thechannel. A dash dot line (FIG. 4) joining the point of connection of fin27 with the leading edge of the following fin has been drawn toillustrate this arrangement.

Without being limitative, the connection line or root is situatedapproximately in the middle of a distance separating two successivefolds of a same zigzag wall.

The flow section of the gas path between fins and opposite walls whichis substantially constant along the whole path of the gas stream in achannel may advantageously represent about 3/5 of the total section ofthe channel. The rear zone 27c of fin 27 further provides guiding of thegas stream. The pressure drops recorded with such an arrangment are muchless important than those obtained with the prior art devices comprisingopen scoops facing the gas flow.

Each fin 27 (FIG. 4) is fixed to a wall 25 by a bent part 30 extendingthe rear zone 27c which matches the exact shape of the wall over alength including the obtuse or concave angled fold 31 succeeding theconvex fold 28 covered by the fin 27. Such an arrangement presentsimportant advantages during the construction of the separator where finsare fixed on wall 25 for example by welding. The accurate positioning ofthe fins is therefore possible assuring and maintaining an accurate andwell defined inlet section of the scoop 29 facing the gas stream, animportant parameter for obtaining optimum efficiency.

In FIG. 3, each zig zag wall 25 has at least four spacer elements 32disposed at the periphery of the walls, each spacer element having anaperture 33 on one side and a stud 34 on the other side; the studs 34 ofthe spacer elements 32 of one wall are arranged for insertion in theapertures 33 of the adjacent wall 25.

The zig zag walls 25 are maintained between two plates (35, 36) one 35of which bears on a first wall 37 of the enclosure 18 and the other ofwhich is pressed by the end 38 of bolts or screws 39 whose thread 40engaged holes in the opposite wall 41 to wall 37 of enclosure 18.

The heads of bolts 39 are joined together by at least a small plate,lame or rod 42. The screws are provided in sufficient number to assurean homogeneous mutual compression of the zig zag walls on each others.

The operation of the steam generator having separators 16 of the typedescribed in the invention is explained hereafter.

The water of the primary coolant circuit of the reactor flows throughthe tubes 3 of the evaporator assembly, the water of the secondarycircuit of the reactor flowing outside tubes 3. The water of thesecondary circuit penetrate through the inlet pite 8 and is distributedover the periphery of the inside of the generator by ring 9.

This water descends along the external enclosure 1, between enclosure 1and the cylindrical casing 4. It naturally rises through the tubesbundle 3 and is vaporized in contact with tubes 3 where the primarycoolant flows, and passes through holes 5 a part of which has beenprovided for this purpose in the spacer plates 6.

The paths then followed by the water-steam emulsion leaving theevaporator assembly 2 are shown by arrows in FIG. 1.

The saturated steam begins by flowing through the cyclone humidityseparators 11 of known type, comprising the fan 12 and a cylindricalwall 13.

By centrifugal extraction due to the forced helical path imposed on thesteam, a part of the water droplets transported thereby is retained onthe internal surface of wall 13 and goes into the water supply zone 10.

This water is mixed with the supply water arriving through pipe 8 andpartially heats it.

The steam, still following the paths shown by the arrows (see also FIGS.2, 3 and 4) penetrates into the separators 16 through their periphery ina rising stream, goes through the separators 16 and leaves the generatorthrough the central steam outlet pipe 17.

When flowing through the separator 16, the liquid particles contained inthe gas stream are trapped by the scoops 29. With the device of theinvention, and even when the gas flow rate is low, the small particlesare stopped. This improved trapping with a low flow rate is due to thedouble change of direction of the flow for each portion of the zig zagwalls having the same direction, i.e. each vertical plane part of thewall or partition located between two successive folds (a concave foldand a convex fold) and to the presence of a constant flow section whichgives to the flow a speed without abrupt changes which are due torestrictions and enlargements in conventional separators.

This flow section is shown by a dot dash line on FIG. 4.

The water thus collected flows down along the fins 27. The rear internalzone of scoop 29 or water spout situated downstream of the summit offold 28 being relatively protected from the gas stream and itsdisturbances, the risk of re-entrainement is minimized. In fact, if thewater collected by the wall travels to the bottom of the bent spout,this arrangement protects the small particles from being re-entrained bythe steam flow. Furthermore, the evacuating downflow section for thecollected water is large, which improves the draining capacity. Thewater falls by gravity into the collecting zone 22 of separator 16 andis removed through pipes 24 which open into the water supply zone 10 ofthe generator.

I claim:
 1. An apparatus for separating entrained liquid particles froma stream of gas which flows in a generally horizontal directioncomprising:an enclosure and a plurality of generally parallel partitionsof zig zag horizontal cross-sectional shape, distributed at evenintervals within said enclosure and defining a plurality ofinter-partition channels constituting respective sinuous travellingpaths for said stream of gas, each of said paths having alternate bends,each of said bends being defined by a concave vertical fold of one ofthe partitions defining the path and a convex vertical fold of the otherpartition defining the path, and each of said convex vertical foldsbeing provided with respective vertically extending channels defining afin, wherein each fin has a first portion covering the respective convexvertical fold, substantially parallel to said respective convex verticalfold and at a distance thereof over a length which is a fraction of thedistance between two successive folds of a same partition, for formingwith said respective convex vertical fold an open scoop having a leadingedge and facing the gas flow and a second portion progressively joiningthe downstream part of the convex vertical fold of the partition coveredconnected to said downstream part along a root line, and fixed to saidpartition, said root line and the leading edge of the next downstreamfin covering the downstream following fold of the same channel beinglocated substantially in the same plane ortogonal to the two partitionsdefining said channel.
 2. An apparatus according to claim 1, whereineach fold of the zigzag partitions is formed by a single bend.
 3. Anapparatus according to claim 1, wherein each fin is connected to thecorresponding partition by a distal end having a bend part which matchesthe shape of said partition over a length including the followingconcave vertical fold succeeding the convex vertical fold covered bysaid fin.
 4. An apparatus according to claim 1, wherein each foldforming bend of the zigzag partitions is a sharp angled dihedron.
 5. Anapparatus according to claim 1, wherein each zigzag partition isprovided with at least four spacer elements disposed at the periphery ofsaid partition, each of the spacing elements having an aperture on oneside and a stud on the other side, the studs of the spacer elements of apartition being arranged for insertion in the corresponding apertures ofthe spacer elements of the adjacent partition for connection.
 6. Anapparatus for separating entrained liquid particles from a stream of gascomprising an enclosure and a plurality of generally parallel partitionsof zig zag horizontal cross-sectional shape distributed at evenintervals within said enclosure and defining a plurality ofinter-partition channels constituting respective sinuous travellingpaths for said stream of gas, each of said paths having alternate bendseach defined by a concave vertical fold of one of the partitionsdefining the path and a convex vertical fold of the other partitiondefining the path, and each of said convex vertical folds being providedwith a respective vertically extending channel defining a fin forming anopen scoop with said partition wherein the fins of a same channel arearranged to define with the opposite corresponding partition of saidchannel a substantially constant flow section for the gas flow all alongthe path of said gas flow in said channel.